240 PROFESSOR OWEN ON THE GENUS DINORNIS. 



The first cursory comparison of the femora, tibiae, &c. sufficed for the recognition of 

 common characters, by which, notwithstanding their very different sizes, they appeared 

 to be generically related to each other, and were readily distinguishable from their ana- 

 logues in the skeletons of the existing Struthious birds. 



A much closer inspection and cautious consideration were obviously required, in order 

 to determine satisfactorily whether the different-sized bones belonged to different-aged 

 birds of the same species, or to distinct species diftering in size. Guided by the seldom- 

 failing law, that distinctive characters are most strongly developed in the peripheral 

 parts of the body, I first collected together and examined the hones of the foot, and for- 

 tunately found for comparison three tarso-metatarsal bones of the same side, the left, 

 and of very different sizes. 



Metatarsi. (Plates XXVII. and XXVIII.) 



I shall first premise the common or generic characters of the tarso-metatarsal bone of 

 the Dinornis, and, in detaiUng the subsequent comparisons of the different- sized bones, 

 shall refer to them, as afterwards to the tibm, femora, &c., by the numbers they bear in 

 the foregoing list, which will obviate much unnecessary repetition. 



The tarso-metatarsai bone of the Dinornis consists of the tarsal and of three primi- 

 tively distinct metatarsals blended together, and forming, as usual, a single bone, divided 

 at the distal extremity into three trochlear articulations, for the three toes. The prox- 

 imal articulation presents two concavities, the inner one the deepest, and the dividing 

 ridge is slightly produced upwards at its anterior termination into a conical obtuse 

 process. At the middle of the back part of the proximal end there are two short and 

 thick longitudinal ridges, divided by a deep round groove for the flexor tendon of the 

 toes : the ridges are supported by a thick longitudinal eminence, which is continued 

 down the middle of the back- part of the bone to a varying distance in the different bones, 

 gradually subsiding as it descends. On each side of the upper part of this median 

 longitudinal eminence there is a foramen, as in most other birds, from which a shallow 

 and narrow longitudinal canal is continued in the larger metatarsi for some distance 

 down the bone : there are no other canals, nor any longitudinal angular ridges at the 

 back part of the metatarsus ; nor is there the slightest trace of a surface for the attach- 

 ment of a hind-toe. On the anterior part of the bone, near the proximal end, there is 

 the usual depression, in which the canals continued from the two posterior foramina 

 terminate by a single foramen : below the depression there is a rough surface, for the in- 

 sertion of the tendon of the tibialis anticus, from which point a median wide and shallow 

 channel extends a certain way down, and divides into two shallower depressions, which 

 diverge to the interspaces of the distal articular condyles : the margins of all these de- 

 pressions are rounded off, and the general surface of the anterior, as of the posterior part 

 of the metatarsus, is smooth and rounded : this, with the great breadth of the bone as 

 compared with the metatarsi of other Struthionidce and tridactyle Grallce, constitutes the 



